Most caulking materials gradually set hard upon contact with the air over a period of time. It is therefore important to keep the material away from the air. This is achieved by a decreasing volume dispenser such as a piston dispenser moving a piston at one end of a tube holding the caulking material. At the other end of the tube is an outlet to which a conically tapering tubular nozzle, usually of plastic, is attached by screw thread. The caulking tubes are purchased with the outlet having a frangible seal so as to prevent the contents from being affected by the atmosphere prior to first use and allow the contents to remain substantially in liquid or viscous form and have a reasonably long shelf life. Materials used are selected such that they are readily applied in viscous liquid form but by contact with air harden or set so as to provide the required caulking. At the end of the tube distal to the outlet is a slidable piston.
The contents of the caulking tube are used by inserting it into a caulking gun so that the nozzle extends from one end of the gun. The caulking gun includes means for forcing a piston rod to move the piston of the tube within the tube and effect expelling or excretion of the contents of the tube out through the nozzle. A trigger mechanism is often employed with the caulking gun which actuates a ratchet mechanism to advance the piston rod engaging the piston to force the caulking material out through the nozzle.
However the material remaining in the nozzle must be in liquid or viscous form or the nozzle outlet will become blocked. Due to the taper and single small nozzle outlet there is the benefit that the material can be dispensed precisely into the required position through the end of the nozzle. The smallness of the nozzle outlet though is also detrimental since it takes very little material to harden in contact with the air in order to block the nozzle outlet. It is therefore important to be able to clear a blocked nozzle.
Generally in known arrangements the nozzle is screwed onto the barrel and is merely a conically tapering tubular plastic nozzle having a single outlet at the tip of the taper. Although users undertaking small "do-it-yourself" projects may have time to disengage the nozzle, clean it by forcing any hardened material back out the larger end of the conically tapering tubular nozzle and reattach the nozzle, professionals using the equipment extensively require their equipment to be always useable and to avoid contamination of the viscous material by small bits of hardened material that may be able to be expelled through the tip of tile nozzle. Often professionals will have a number of nozzles and merely dispose of any blocked nozzle rather than cleaning the nozzle. The professional will use a large number of nozzles without ever using any one nozzle for its entire useful lifetime
Whether the nozzle is being cleaned or being replaced there is also a large loss of material since the entire contents of the nozzle must be discarded in each of these cleaning methods although only the material at the tip of the nozzle may have hardened.
Many types of nozzles have been devised and shown in the patent literature. However, few documents disclose apparatus that simplify cleaning and reusing of a nozzle. They include published international patent no. WO 93/24030 showing an enamel applicator and doser plug in which a lever arm pushes a central pin down the nozzle to force liquid through the nozzle; patent No. JP 60-255163 showing a cylindrical stirring nozzle for a different purpose of a two component adhesive and which opens in half along an entire longitudinal seam for removal of all of the unused two components in the nozzle since all will have hardened in the internal pockets of the nozzle when the two components were mixed. However the nozzle does not allow part cleaning without allowing air contact with the rest of the material in the nozzle and is very likely to break or not properly close for reuse; and published Australian patent application no. AU-A-56253/96 for a nozzle with two nozzle parts that attach end to end but is very similar to unscrewing a standard nozzle to clean.
Some published patent documents show a slit in a nozzle for particular means of applying a liquid in a particular way such as U.S. Pat. No. 5,553,758--nozzle adaptor for applying hot melt adhesive; WO 97/41968--deposition of beads of material; WO 96/404--45 article for applying and spreading viscous material and method thereof; U.S. Pat. No. 5,059,050--dispenser for hair treatment solutions; AU-A-74044/87--pen-like dispenser for applying rust converting liquid; and WO 96/33025--silicone paint brush artist's tool.
Another group of documents disclose caps for nozzles but particularly caps allowing variable amount of flow such as U.S. Pat. No. 4,967,941--twist lock adjustable metering closure cap; and U.S. Pat. No. 4,213,546--cap for the nozzle of a caulking cartridge. However none of these documents show a means of cleaning and reuse of the nozzle.